scroll vrs. recip. compressor question

[okie]

On a txv system with a recip. compressor do you need a start capacitor?

On a scroll compressor with a txv do you need a start capacitor?

[rickboggs]

Yes and yes... kick start

[beenthere]

Scrolls don't need a start cap.
But it doesn't hurt if they have one.

[rickboggs]

beenthere is right

[danglerb]

Do I have this confused, mostly I hear about using a "hard start kit" with a txv, and all compressors us a combined run/start cap don't they?

[comfortdoc]

txv + hard start kit = mostly, but not always
all compressor use combined run/start cap - nope

[t527ed]

have never put start kit on scroll compressor. 99.99% of my units are lennox scroll units with txv. have been using scroll units since they came out around 1990.

[rickboggs]

The refrigerant does not equalize when a reed compressor is matched with a txv, therefor the compressor starts under a load... ya need a kick

I was was wrong about the scroll. I should have yep and nope.

[Mr Bill]

Originally posted by t527ed
have never put start kit on scroll compressor.

Ruud and Rheem puts one on "every" one of there 14 seer units must be doing it for some reason, or it could be maybe they just like to spend the extra money, yea thats it. :D

[t527ed]

Originally posted by mrbillpro

Originally posted by t527ed
have never put start kit on scroll compressor.

Ruud and Rheem puts one on "every" one of there 14 seer units must be doing it for some reason, or it could be maybe they just like to spend the extra money, yea thats it. :D


have never seen or put one on a lennox unit. maybe they are using different txv's???? as i said i have been installing lennox units with scrolls since 1990. to date i may have had 6 compressor failures.

[riderman]

I think I undestand the reason for a "hard start kit" for 14 SEER units with a TX valve based on coments from here.

I was taught that a hard start kit was a bandaid for worn compressors essentially on their way out.

Why arent NEW high SEER units designed with a cap or compressor to handle the designed start up load?

Old compressor technology?

Just wondering...

[beenthere]

Recip compressors for A/C, H/P applications are made with low torque starting motors, Even with a TXV that equalizes most of them need a start cap.


Start, run caps are seperate things. Duel caps are run caps for both the compressor and fan.

[okie]

thanks for the comments

[behappy]

I have noticed that "most" of the high end scroll systems now come with a "start kit".

[RoBoTeq]

Originally posted by riderman
I was taught that a hard start kit was a bandaid for worn compressors essentially on their way out.


You were taught wrong.

[smadave]

You need a hard start if:

1. Hard shut off TXV

2. Long Lineset

3. Low ambient conditions

4. Voltage problems


Dave in NJ

[beenthere]

Originally posted by smadave
You need a hard start if:

1. Hard shut off TXV

2. Long Lineset

3. Low ambient conditions

4. Voltage problems


Dave in NJ

Scrolls start with out hard start kits even against non bleed TXV's.

[docholiday]

The truth of the matter is, a start kit in most scroll applications is a bullet point or a selling feature. Its something that can be added to a spec to make the use of lower end equipment require adding to. Now, if you are going to run these obnociously long linesets, it's something you might add to a scroll, but in fairness, its not required often at all. In reality, the money would be better spent on LPS, HPS, CCH, and even Driers.

Yes, some recips with non-bleed TXV's need start componants, but even the Benchmark Recip, has built in features that can overcome that need.

[smithone]

Yes, residential scroll compressors do have capacitors in which specifications are found in Copeland Electrical Handbook 2005-2006 Edition.


[Edited by smithone on 07-23-2006 at 04:02 PM]

[jasond1011]

as per mfg recommendation. all scrolls and receips should have a hard start kit installed. scrolls and receps are equiped with non equalizing txvsand a start cap is therefore recommended on both. checkvalve in compressor prevents bleeding back and balancing pressure on the scrolls.

[mark beiser]

Scroll compressors have more internal mechanical friction to overcome on startup, so the inrush current tends to be higher than the same size recip, which in a changout situation, can result in more noticeable light dimming in the house when the compressor starts. This is a common complaint in some areas.
A start kit on a scroll compressor reduces the length of time the motor pulls LRA, which reduces the lights dimming in the house when the compressor starts.
Some manufacturers also require a start kit for scroll compressor equipped systems that are used for low ambient cooling.

[BaldLoonie]

Rheem's 13 SEER units come factory with start kit. RAND/RPNE. Looking at A-S 13 SEER, only the 3 ton and 5 ton have scrolls. The 3 ton does not have a kit, the 5 ton does. We had some complaints about lights dimming with A-S scrolls in the past and the distributor would give us a free start kit in those cases.

[ga-hvac-tech]

Scroll compressors have more internal mechanical friction to overcome on startup, so the inrush current tends to be higher than the same size recip, which in a changout situation, can result in more noticeable light dimming in the house when the compressor starts. This is a common complaint in some areas.
A start kit on a scroll compressor reduces the length of time the motor pulls LRA, which reduces the lights dimming in the house when the compressor starts.
Some manufacturers also require a start kit for scroll compressor equipped systems that are used for low ambient cooling.

Hey Mark,

I was in a 'counter conversation' with another tech on this topic a while back. They suggested that a start kit on a scroll would increase the energy efficiency. Seemed to me that if it lowered the light dimming, it would also lower the KWH's used... Any thoughts? THX in advance!

[mark beiser]

Hey Mark,

I was in a 'counter conversation' with another tech on this topic a while back. They suggested that a start kit on a scroll would increase the energy efficiency. Seemed to me that if it lowered the light dimming, it would also lower the KWH's used... Any thoughts? THX in advance!

Well, the start kit doesn't lower the peak LRA, but it does shorten the time the motor is at LRA, so I would have to agree that it does improve the efficiency, however slightly.

And before someone jumps in and says that a start kit lowers the peak LRA of the motor on startup, and points to their amp meter readings, your meter doesn't have a fast enough response time to show you the true peak amperage on startup. You get a lower reading because it pulls LRA for less time, so the amperage has dropped off more before your meter displays anything.

[zeetammie]

..

[beenthere]

Do a search on screen name payson.
He has a link to a video of the amp draw of a compressor with and without hard start kit.
And of different start kits.

[Airmechanical]

have never seen or put one on a lennox unit. maybe they are using different txv's???? as i said i have been installing lennox units with scrolls since 1990. to date i may have had 6 compressor failures.

only 6 lennox compressor failures in 18 years

they must be calling someone else!



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